A higher difficulty changes the way you play a game. Just try running around out in the open in Call of Duty on the Veteran difficulty, you'll die immediately. In STALKER, you'll get killed by a single bullet which means you need to use guerrilla tactics and cover.
I agree with Nickelback being a shitty band though.
Why do you want to kill WW2 games? That's just stupid, we've probably killed just as many terrorists in video games as Nazis. Modern warfare games are played out too.